Neandertals used fire-making tools 400,000 years ago

artifact: Some human-made object (such as a pot or brick) that can be used as one gauge of a community’s culture or history.

chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H₂O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

clay: Fine-grained particles of soil that stick together and can be molded when wet. When fired under intense heat, clay can become hard and brittle. That’s why it’s used to fashion pottery and bricks.

colleague: Someone who works with another; a co-worker or team member.

digest: (noun: digestion) To break down food into simple compounds that the body can absorb and use for growth. Some sewage-treatment plants harness microbes to digest — or degrade — wastes so that the breakdown products can be recycled for use elsewhere in the environment.

evolution: (v. to evolve) A process by which species undergo changes over time, usually through genetic variation and natural selection. These changes usually result in a new type of organism better suited for its environment than the earlier type. The newer type is not necessarily more “advanced,” just better adapted to the particular conditions in which it developed. Or the term can refer to changes that occur as some natural progression within the non-living world (such as computer chips evolving to smaller devices which operate at an ever faster speed).

fire: The burning of some fuel, creating a flame that releases light and heat.

Homo erectus: An extinct species of hominid that lived in Africa and Eurasia between about 1.9 million and 70,000 years ago.

ice age: Earth has experienced at least five major ice ages, which are prolonged periods of unusually cold weather experienced by much of the planet. During that time, which can last hundreds to thousands of years, glaciers and ice sheets expand in size and depth. The most recent ice age peaked 21,500 years ago, but continued until about 13,000 years ago.

iron: A metallic element that is common within minerals in Earth’s crust and in its hot core. This metal also is found in cosmic dust and in many meteorites.

milestone: An important step on the road to stated goal or achievement. The term gets its name from the stone markers that communities used to erect along the side of the road to inform travelers how far they still had to go (in miles) before reaching a town.

Neandertal: A species (Homo neanderthalensis) that lived in Europe and parts of Asia from about 200,000 years ago to roughly 28,000 years ago.

paleolithic: An adjective meaning old stone, it refers to the early Stone Age. This period began about 750,000 years ago and ended about 200,000 years ago. A hunter-gather period, it predates when people began farming.

predator: (adjective: predatory) A creature that preys on other animals for most or all of its food.

pyrite: A common iron-bearing mineral that cannot permanently hold a magnetic field but is weakly attracted to magnets. As shown in its chemical formula, each molecule of pyrite (FeS 2 ) is made of one iron (Fe) atom and two sulfur (S) atoms.

remnant: Something that is leftover — from another piece of something, from another time or even some features from an earlier species.

residue: A remnant or material that is left behind after something has been removed. For instance, residues of paint may remain behind after someone attempts to sand a piece of wood; or sticky residues of adhesive tape may remain on the skin after a bandage is removed; or residues of chemicals may remain in the blood after exposure to a pollutant.

sediment: Material (such as stones and sand) deposited by water, wind or glaciers.

shard: A piece of broken pottery, tile or rock, or a hard, broken piece of anything that has an irregular shape.

skeptical: Not easily convinced; having doubts or reservations.

tool: An object that a person or other animal makes or obtains and then uses to carry out some purpose such as reaching food, defending itself or grooming.

toxin: A poison produced by living organisms, such as bacteria, algae and certain plants (such as poison ivy). Bees, spiders, snakes and other animals also produce toxic materials. These are referred to as venoms.